In a Long-Term Evolution (LTE) system, when a User Equipment (UE) is connected in, a base station allocates necessary parameters for the UE, such as security algorithm, configuration parameters for a medium access control layer (Layer 2), configuration parameters for a physical layer (Layer 1), and configuration parameters for a radio link control layer (Layer 3), for example, radio link failure parameters. Regarding an established bearer, the base station should be aware of information about a channel between the bearer and a core network (i.e., a GTP tunnel). All the parameters mentioned above are called UE context information.
In 3GPP Release 13, for some low-cost UE, established services are generally services with time delay tolerant. To reduce signaling overhead for accessing a network, a Radio Resource Control (RRC) suspend or resume mechanism is introduced. In this mechanism, a UE when turning from a connected state to an idle state should save context information configured for accessing a network currently, a base station saves the context information of the UE which includes configuration parameters for an access layer of the UE, and further Mobility Management Entity (MME) in a core network also saves the context information of the UE which includes configuration parameters for a non-access layer of the UE, GTP tunnel and so on.
When the UE is indicated to enter the idle state, the base station sends a certain identification to the UE, called Resume ID. When the UE is accessed to the network again, the UE initiates a connection resume procedure to indicate its Resume ID to the base station. The base station identifies the UE according to the Resume ID, and resumes a service tunnel (including GTP tunnel at interface S1 and data radio bearer at a corresponding air interface) established for the UE formerly using the saved context information of the UE. In this way, the UE can perform data transmission through the service tunnel again. In the above procedure, there is no need to configure radio resources repeatedly, which greatly reduces signaling overhead.
However, the UE cannot determine whether the selected base station supports the resume procedure, thus, the existing resume mechanism may cause failure in the connection resume procedure.